Has anyone tried these? I'm particularly interested how good they are and containing ebf poo.

I have a stash of KL0s and XS BG Bamboo Fitteds and was trying to supplement with something cheaper to get up to about 2 dozen diapers. I know prefolds are cheap but the poo gets all over the cover doesn't it?

Any good fitted or prefitted, properly put on, should keep poo off the covers. Jellyrolled PFs totally contain the poo for me, and I'm not even great at the fold since I only use PFs if necessary or laundry day, usually.